1 It's your body's largest organ, despite what the readers of Maxim think.
2 An average adult's skin spans 21 square feet, weighs nine pounds, and contains more than 11 miles of blood vessels.
3 The skin releases as much as three gallons of sweat a day in hot weather. The areas that don't sweat are the nail bed, the margins of the lips, the tip of the penis, and the eardrums.
4 Ooh, that smell: Body odor comes from a second kind of sweat—a fatty secretion produced by the apocrine sweat glands, found mostly around the armpits, genitals, and anus.
5 Yum! The odor is caused by bacteria on the skin eating and digesting those fatty compounds.
6 Breasts are a modified form of the apocrine sweat gland.
7 Fetuses don't develop fingerprints until three months' gestation.
8 Without a trace: Some people never develop fingerprints at all. Two rare genetic defects, known as Naegeli syndrome and dermatopathia pigmentosa reticularis, can leave carriers without any identifying ridges on their skin.
9 Fingerprints increase friction and help grip objects. New World monkeys have similar prints on the undersides of their tails, the better to grasp as they swing from branch to branch.
10 Blowin' in the wind: Globally, dead skin accounts for about a billion tons of dust in the atmosphere. Your skin sheds 50,000 cells every minute.
11 There are at least five types of receptors in the skin that respond to pain and to touch.
12 One experiment revealed that Meissner corpuscles—touch receptors that are concentrated in the fingertips and palms, lips and tongue, nipples, penis and clitoris—respond to a pressure of just 20 milligrams, the weight of a fly.
13 In blind people, the brain's visual cortex is rewired to respond to stimuli received through touch and hearing, so they literally "see" the world by touch and sound.
14 "In the buff" became synonymous for "nude" in 17th-century England. The term derives from soldiers' leather tunics, or "buffs," whose light brown color apparently resembled an Anglo-Saxon backside.
15 White skin appeared just 20,000 to 50,000 years ago, as dark-skinned humans migrated to colder climes and lost much of their melanin pigment.
16 I see very, very white people: Albinos are often cast as movie villains, as seen in The Da Vinci Code, Die Another Day, The Matrix Reloaded, and—inexplicably—the 2001 flick Josie and the Pussycats. Robert Lima of Penn State suggests that people associate pale-skinned albinos with vampires and other mythical creatures of the night.
17 More than 2,000 people have radio frequency identification chips, or RFID tags, inserted under their skin. The tags can provide access to medical information, log on to computers, or unlock car doors.
18 Flesh for fantasy: At the Baja Beach club in Barcelona, customers can get an implanted RFID "debit card" and party until their funds are exhausted.
19 The Cleveland Public Library, Harvard Law School, and Brown University all have books clad in skin stripped from executed criminals or from the poor.
20 Hopefully, they didn't have to reprint it: One such volume is Andreas Vesalius's pioneering 16th-century work of anatomy, De Humani Corporis Fabrica (On the Fabric of the Human Body).
20 Things You Didn't Know About...Leonardo da Vinci
by Jason Stahl and Alex Stone
1 Leonardo was the love child of Caterina, a peasant, and Ser Piero, a lawyer and landlord. He was homeschooled and lacked a formal education in Greek and Latin.
2 He was an accomplished lyre player. When he was first presented at the Milanese court, it was as a musician, not an artist or inventor.
3 Leonardo narrowly beat a sodomy rap—possibly involving one of his male models—brought against him by Florentine officials.
4 Mona Lisa theory #1: Her smile means she was secretly pregnant.
5 Theory #2: She was amused by the musicians and clowns who entertained her while Leonardo painted her. (Another theory says the Mona Lisa is a portrait of Leonardo himself, slyly disguised. But you'd heard that one before, hadn't you?)
6 Columbia University art historian James Beck retorts, "As sure as the moon is not made of green cheese, this is not da Vinci in drag."
7 Then again, unusual for a painter, Leonardo left no definitive image of himself.
8 Of course, that was before she saw the picture: Researchers at the University of Amsterdam and the University of Illinois used face-recognition software to determine that the Mona Lisa is 83% happy, 9% disgusted, 6% fearful, and 2% angry.
9 Bill Gates bought the Codex Leicester in 1995 for $30 million. This manuscript, the only one not held in Europe, includes da Vinci's studies on hydraulics and the movement of water.
10 And Leonardo loved water: He developed plans for floating snowshoes, a breathing device for underwater exploration, a life preserver, and a diving bell that could attack ships from below. In case one had to.
11 Leonardo was the first to explain why the sky is blue. (It's because of the way air scatters light.)
12 And he figured out why the entire moon is dimly visible when it is a thin crescent. Its nightside is lit by light reflected from Earth, which appears 50 times brighter from the moon than the full moon appears here.
13 An ambidextrous, paranoid dyslexic, Leonardo could draw forward with one hand while writing backward with the other, producing a mirror-image script that others found difficult to read—which was exactly the point.
14 The Louvre recently spent $5.5 million rehanging the Mona Lisa inside a display case set into a wall, six feet behind a wooden barrier.
15 In August 2003, da Vinci's Madonna of the Yarnwinder, valued at $65 million, was stolen from Drumlanrig Castle in Scotland by two men posing as tourists. They escaped in a Volkswagen Golf.
16 Leonardo designed an armored car, a scythed chariot, a pile driver, a revolving crane, a pulley, a lagoon dredge, and a flying ship.
17 In December 2000, skydiver Adrian Nicholas landed in South Africa using a parachute built from one of Leonardo's designs.
18 I wonder what happens if . . . After dissecting cadavers, Leonardo replaced the muscles with strings to see how they worked.
19 Sometimes he could be such a dick: He was a big fan of puns and word games, and Folio 44 of his Codex Arundel contains a long list of playful synonyms for penis.
20 He crushed intelligent design before anyone even thought of it: His studies of river erosion convinced him that the Earth is much older than the Bible implies, and he argued that falling sea levels—not Noah's Flood—left marine fossils on mountains